1. Field of the Invention
The present invention relates to an automotive power source apparatus that detects the voltages of batteries making up the driving battery that drives a vehicle, that is further provided with circuitry to detect over-charging and over-discharging of those batteries, and relates to a vehicle equipped with the power source apparatus.
2. Description of the Related Art
An automotive power source apparatus detects the voltages of batteries making up the driving battery, and controls driving battery charging and discharging while protecting the batteries. This type of power source apparatus has a plurality of batteries connected in series to increase output voltage and attain high power output. The voltage of each battery is detected and charging and discharging are controlled while monitoring over-charging, over-discharging, and voltage balance between batteries. If voltage imbalance develops between batteries, a certain battery or batteries can be easily over-charged or over-discharged. Over-charging and over-discharging markedly degrade battery characteristics and significantly reduce battery lifetime. Additionally, an automotive power source apparatus has been developed with two circuits to detect battery voltage and further increase reliability with redundancy.
Refer to Japanese Laid-Open Patent Publication 2008-125236.
If one of the circuits malfunctions in an automotive power source apparatus that detects battery voltage with two circuits, voltage can still be detected with the other circuit thereby improving reliability. The circuits that detect battery voltage could be powered by the 12V auxiliary battery (accessory battery) installed in the vehicle. However, such a circuit configuration requires the driving battery ground line to be connected to the vehicle chassis ground. If the driving battery ground line is connected to the vehicle chassis ground, the high-voltage driving battery cannot be isolated from chassis ground and it becomes difficult to insure safety and prevent electric shock.
This drawback can be resolved by supplying power from the driving battery to operate the circuits that detect voltage in the driving battery, and isolating signals output from those circuits to the vehicle-side via an isolation circuit. However, this circuit configuration has the drawback that if the isolation circuit malfunctions, battery voltage signals cannot be transmitted to the vehicle-side even though the circuits that detect voltage may be operating properly.
The present invention was developed with the object of further resolving the drawbacks described above. Thus, it is a primary object of the present invention to provide an automotive power source apparatus and vehicle equipped with the power source apparatus that can more reliably and stably transmit battery voltage signals to the vehicle-side while insuring safety by isolating the driving battery from the vehicle chassis ground.